I think they need to introduce a big patch soon. Meta has been very stale lately, every role has a clear winner.

I think it mainly comes down to Blizzard's Support and Tanks philosophy. In early days they tried to create both Supports and Tanks that could do little bit of everything, but now they try to push them into niche positions. Double Warrior meta has risen in popularity because all new Warriors have been Bruisers who are very strong in certain situations and have comparable damage to survivability ratio to melee Assassins while providing more safety to backline. Also Double Support + Hyper Carry is on a rise because Blizzard refuses to give Cleanse to new Supports which is major factor in competitive and Bruisers deal enough damage to compensate for lack of Assassins/Specialists.

I think we need more main Tank Heroes, Bruisers dealing less damage, doing something about Cleanse and reduce power level of meta defining Heroes.

How they can fix tha problem?

Healing is either broken op or useless.
The healing itself is a problem, there has to be a situational healer hero, not a mandatory core role. That is a design misstep. Again I believe its far too late to change it, even though it can be done very quickly and easily.
I know people like to think that all the roles should be as impactful as one another, but damage dealers will always be king of damage, and making them unfun has serious consequences.

Healing is either broken op or useless.
The healing itself is a problem, there has to be a situational healer hero, not a mandatory core role. That is a design misstep. Again I believe its far too late to change it, even though it can be done very quickly and easily.
I know people like to think that all the roles should be as impactful as one another, but damage dealers will always be king of damage, and making them unfun has serious consequences.

Actually, I don't think healing is the problem.

Current problem with Supports is they are overly specialized, but I think their Healing numbers are fine. Right now it easy to get punished in draft if you pick a certain Support early. For example you draft Uther first and suddenly enemy team picks Lunara + Malthael rot composition, no matter how good is rest of your composition, Uther just won't be able to stop the bleeding. I like they gave supports some niche, but all of them should have talent options to deal with all situations to a lesser extent.

However I think the biggest issue is Bruisers being overtuned. I just don't really see much need to pick Melee Assassins because Warriors do comparable damage over the length of battle, are harder to punish thanks to their health pools while also bringing a ton of utility. On top of that, most of them are really strong solo laners.

This created a Double Warrior meta because you have Warriors who can soak two lanes, hold a solo lane and be impactful in team fights because they provide good anti-dive protection for backline and provide a good amount of CC or utility. I think Warriors should keep their overall utility, but need to do way less damage because they are taking job of melee Specialists and Assassins.

Just look at current meta, the only melee Assassin with a decent popularity is Illidan because he can actually match Dehaka, while having much better map pressure due the cooldown reduction from AAs on Hunt and ability to push structures harder. He sits at 65% popularity in both Clashes while next popular melee Assassin is Malthael who can counter Double Warrior meta at 9% in Western Clash and at 23% in Eastern Clash. Now look at Specialists and we can safely say the only decent melee Specialist is Xul and yet he was only banned once in Eastern Clash, but had 11% popularity in Western Clash.

Thanks to making Supports more niche and rise of Double Warrior meta, the Double Support became a thing. Usually you see a sustain Healer being paired with Burst preventing Support. It is very good at dealing with slower damage of Double Warrior and overall skirmishing while also shutting dive.